This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-078517, filed Mar. 19, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method and an apparatus for measuring, analyzing and evaluating the correlation between electrical properties and structural characteristics of a semiconductor device by using an X-ray beam.
2. Description of the Related Art
As a method for evaluating electrical properties of a semiconductor device, there is known a so-called DLTS (Deep Level Transient Spectroscopy) method or an ICTS (Isothermal Capacitance Transient Spectroscopy) method. Electrical properties of impurities or defects in the semiconductor can be obtained by using the DLTS method or the ICTS method. However, information concerning an internal structure of the semiconductor or electron states of a conduction band in a vicinity of a defect in the semiconductor can not be acquired. Further, it is impossible to select a specific type of atom or element from multiple kinds and a plurality of atoms or elements in a semiconductor, and to excite the inner shell of the specific type of atom or element in order to obtain information thereof. Therefore, it is almost impossible to clarify the correlation between the fine structures of impurities, defects, or the vicinity of them in the semiconductor and their electrical properties by using the DLTS method or the ICTS method.
As means for observing the fine structure or electron states at the atomic scale of a sample by using electrical means, there is, for example to be measured, a scanning tunneling microscope (STM). However, although STM can observe the structure or electron states of a surface layer portion of the sample, it can hardly observe the inside of the sample. Furthermore, the sample that STM can observe is restricted to a conductive sample base d on the measurement principle of STM. In case of using STM to observe an insulator, the surface of the insulator must be coated with a conductive material, and the original surface structure of the insulator is deteriorated. Thus, STM can hardly finely observe at the atomic scale the structure or electron states of an insulating film provided in the semiconductor device.
Moreover, as a method for finely and accurately analyzes the internal structure or electron states of the sample at the atomic scale without using electrical means, there is known, for example, an X-ray absorption fine structure (XAFS) method that analyzes the structure by using X-rays. This XAFS method is one type of the absorption spectrum method, and roughly divided into two types, i.e., an X-ray absorption near-edge structure (XANES) method and an extended X-ray absorption fine structure (EXAFS) method. A combined use of the XANES method and the EXAFS method can finely analyze the structure or electron states of various materials contained in a sample, at the atomic scale. The XANES method or the EXAFS method is, however, exclusively used for analysis of the fine structure of a sample to be measured and rarely used for analysis of electrical properties of a sample.
Therefore, the highly reliable evaluation method or evaluation apparatus that can measure and analyze structural characteristics and electrical properties of the semiconductor by associating them with each other, and clarify the relationship between structural characteristics and electrical properties is not substantially established.
It is an object of the present invention to provide an evaluation method and an evaluation apparatus for a semiconductor device which can accurately measure, analyze and evaluate electrical properties, structural characteristics and electron states of a semiconductor device by using an X-ray beam, and can clarify the correlation between electrical properties, structural characteristics and electron states of a semiconductor device with the high reliability, irrespective of a part of the semiconductor device to be measured or a material to be measured.
According to one aspect of the present invention, there is provided a method for evaluating a semiconductor device, comprising the steps of: evaluating electrical properties of a semiconductor device by measuring and analyzing a junction capacitance of a semiconductor provided in the semiconductor device and a transient change of the junction capacitance while applying an X-ray beam to the semiconductor device intermittently; and evaluating a structure and electron states of the semiconductor by measuring and analyzing an energy spectrum of an X-ray beam absorbed into an element present in the semiconductor while applying an X-ray beam to the semiconductor device continuously.
According to the present invention, electrical properties, a structure and electron states of a semiconductor provided in a semiconductor device can be measured, analyzed and evaluated by using an X-ray beam that is being set an appropriate application mode of it to the semiconductor device, in accordance with an evaluating purpose for the semiconductor device. Therefore, electrical properties, structural characteristics and electron states of the semiconductor device can be analyzed and evaluated with the high accuracy, and the relationship between them can be clarified with the high reliability.
According to one aspect of the present invention, there is provided an apparatus for evaluating a semiconductor device, comprising: an X-ray beam applying device which applies an X-ray beam to a semiconductor device; an X-ray beam application-time setting device which switches a mode of applying the X-ray beam to the semiconductor device, between an intermittent application mode and a continuous application mode, and which sets an X-ray beam application-time to prescribed values; a junction capacitance detecting device which detects a junction capacitance of a semiconductor provided in the semiconductor device and a transient change of the junction capacitance while the X-ray beam is being intermittently applied to the semiconductor device; a junction capacitance measurement device which measures the junction capacitance and the transient change thereof, both detected by the junction capacitance detecting device; a first evaluation device which analyzes the junction capacitance and the transient change thereof, both measured by the junction capacitance measurement device and which evaluates electrical properties of the semiconductor device; an X-ray spectrum detecting device which detects an energy spectrum of the X-ray beam continuously applied to and absorbed into an element present in the semiconductor, while the X-ray beam is being continuously applied to the semiconductor device; an X-ray spectrum measurement device which measures the energy spectrum detected by the X-ray beam spectrum detecting device; and a second evaluation device which analyzes the energy spectrum measured by the X-ray beam spectrum measurement device and which evaluates a structure and electron states of the semiconductor device.
According to the present invention, electrical properties, a structure and electron states of a semiconductor provided in a semiconductor device can be measured, analyzed and evaluated by using an X-ray beam that is being set an appropriate application mode of it to the semiconductor device, in accordance with an evaluating purpose for the semiconductor device. In addition, such setting of the appropriate application mode of the X-ray beam, and measurement, analysis and evaluation by using the X-ray beam can be carried out by one apparatus. Therefore, electrical properties, structural characteristics and electron states of the semiconductor device can be analyzed and evaluated with the high accuracy, and the relationship between them can be clarified with the high reliability.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.